Succ (Eq ("a", "a"))
Succ (Eq (Mul ("a", "a"), Mul ("a", "a")))
Succ (Eq (Add (Mul ("a", "a"), Sub (Div ("a", "a"), Mul ("a", "a"))), Sub (Mul ("a", "a"), "a")))
Fail ({""*" expected at"}, 1, 2)